Yalantis/uCrop · error · CImgArgumentException

"[" cimg_appname "_math_parser] CImg<

Error message

"[" cimg_appname "_math_parser] CImg<%s>: Function 'sort()': Arguments 'nb_elts=%g' and 'siz_elt=%g' are invalid for sorting a vector of size %u."

What it means

The math parser 'sort()' function sorts a vector in blocks: nb_elts blocks of siz_elt values each. The product siz_elt*nb_elts must not exceed the vector size 'siz', and siz_elt must be >= 1; otherwise a CImgArgumentException reports the conflicting nb_elts/siz_elt values against the actual vector size.

Solutions

Ensure siz_elt >= 1 and ceil-based nb_elts so that nb_elts*siz_elt <= siz: pass nb_elts = siz/siz_elt (integer division).
Recompute block parameters from the actual vector size instead of hard-coding them.
If the goal is a full sort, use the simpler one-argument sort form rather than block parameters.
Catch CImgArgumentException and log the vector size to select correct block parameters.

Example fix

// before: sort(V, 10, 4)  // 40 > 32 elements
// after:  sort(V, 8, 4)    // 8*4 = 32

Defensive patterns

Strategy: validation

Validate before calling

if (siz_elt < 1 || siz_elt * nb_elts > siz)
  throw std::runtime_error("sort block parameters do not fit vector size");

Try / catch

try { img.evaluate(sortExpr); } catch (const CImgArgumentException& e) { log("sort() params invalid: " << e.what()); }

Prevention

Derive nb_elts = siz / siz_elt instead of hard-coding
Assert siz_elt >= 1 before building the expression
Re-derive block parameters whenever vector size changes

When it happens

Trigger: sort(ptr,siz,...,nb_elts,siz_elt,sort_index) where nb_elts*siz_elt > siz (e.g. sorting 10 blocks of 4 on a vector of 32) or siz_elt == 0, typically because block parameters were hard-coded and the vector dimension changed.

Common situations: Changing vector length (e.g. after resizing a feature vector) without updating sort block parameters; passing 0 or negative-derived siz_elt; computing nb_elts from a formula that over-estimates.

Understand the failure class

Background: "Must be a positive integer", "Invalid value", "Unsupported": the invalid-argument-value error family, when a library rejects the value you pass — this error's family across 35 libraries.

Related errors

AI-assisted analysis of Yalantis/uCrop@f788b534b4 (2026-09-08). Data as JSON: /api/errors/1b066711208377e5. Report an issue: GitHub.

Appendix: source

Thrown at ucrop/src/main/jni/CImg.h:29782

          m = (unsigned int)mp.opcode[6];
        const bool use_LU = (bool)_mp_arg(7);
        CImg<doubleT>(ptrd,m,k,1,1,true) = CImg<doubleT>(ptr2,m,l,1,1,false).
          solve(CImg<doubleT>(ptr1,k,l,1,1,true),use_LU);
        return cimg::type<double>::nan();
      }

      static double mp_sort(_cimg_math_parser& mp) {
        double *const ptrd = &_mp_arg(1) + 1;
        const double *const ptrs = &_mp_arg(2) + 1;
        const bool is_increasing = (bool)_mp_arg(4);
        const unsigned int
          siz = (unsigned int)mp.opcode[3],
          nb_elts = mp.opcode[5]==~0U?siz:(unsigned int)_mp_arg(5),
          siz_elt = (unsigned int)_mp_arg(6),
          sort_index = std::min((unsigned int)_mp_arg(7),siz_elt - 1);
        const ulongT sn = siz_elt*nb_elts;
        if (sn>siz || siz_elt<1)
          throw CImgArgumentException("[" cimg_appname "_math_parser] CImg<%s>: Function 'sort()': "
                                      "Arguments 'nb_elts=%g' and 'siz_elt=%g' are invalid "
                                      "for sorting a vector of size %u.",
                                      mp.imgin.pixel_type(),_mp_arg(5),_mp_arg(6),siz);
        CImg<doubleT>(ptrd,siz_elt,nb_elts,1,1,true) = CImg<doubleT>(ptrs,siz_elt,nb_elts,1,1,true).
          shift(-(int)sort_index,0,0,0,2).get_sort(is_increasing,siz_elt>1?'y':0).shift((int)sort_index,0,0,0,2);
        if (sn<siz) CImg<doubleT>(ptrd + sn,siz - sn,1,1,1,true) = CImg<doubleT>(ptrs + sn,siz - sn,1,1,1,true);
        return cimg::type<double>::nan();
      }

      static double mp_sqr(_cimg_math_parser& mp) {
        return cimg::sqr(_mp_arg(2));
      }

      static double mp_sqrt(_cimg_math_parser& mp) {
        return std::sqrt(_mp_arg(2));
      }

      static double mp_srand(_cimg_math_parser& mp) {

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